Field of the Invention
The invention relates to a method of manufacturing an effective electric point of contact at the end of an electrical line, which comprises a plurality of aluminum or aluminum alloy.
Description of the Related Art
Such a method is essentially described, for example, in EP 2 735 397 A1.
The conductor to be processed by the method according to the invention can be comprised of aluminum or an aluminum alloy. For simplicity's sake, only aluminum is mentioned in the following, however it can also mean an aluminum alloy. The word “stranding” means particularly the concept of “twisting” but also of “contorting” or generally of “holding together.”
Conductors of aluminum have been increasingly used as substitutes for copper conductors on the grounds of weight and cost. Principal areas of use of these conductors are, for example, automobile and airplane technology. The lower electrical conductivity of the aluminum as opposed to copper is of no significance for most uses. Problems arise from connecting contact points to the conductor because the aluminum conductors are coated in a poorly electrically conductive oxide layer. This deficiency becomes especially apparent with the existence of a plurality of individual strands, also referred to as strand conductor strands from which each, without special treatment, is surrounded by an unavoidable oxide layer. This problem has been known for a long time and described in many printed publications. They refer specially to processes with which the oxide layers can be broken and/or replaced with additives to make it possible for all wires to have a strand conductor to connect with the electrical current. The oxide remains, but as a harmful part at the end of the conductor. The following five documents are mentioned as examples.
In DE 102 23 397 B4 a method is disclosed in which a contact element establishes a good electric connection connected to a strand conductor composed of aluminum wires. In addition, a tin plated metallic sleeve is initially pushed onto the inner side of the end of the strand conductor. The individual wires would then be tin plated or soldered by means of protective gas welding or ultrasonically on their front side. The surrounding oxide layer of the strand conductor will thereby be broken up. The result is a cover-type tin plating or welding on the end of the strand conductor. Finally, the contact element is pushed on and pressed together with the end of the strand conductor. The cover-type tin plating or welding is excluded from the pressing.
DE 103 46 160 B3 describes a method for contacting a strand conductor completed as an aluminum conductor in which on the end of the aluminum conductor on the inner side is pushed a tin plated, for example copper composed, contact terminal. The completed pipe-shaped contact terminal is placed on the front end of the aluminum conductor by means of ultrasonic tinning or by means of a known metal welding method.
In the method according to DE 103 57 048 A1, a supply of contacting means is placed on the end of an aluminum composed strand conductor and is heated at least up to its melting temperature. Using the contacting means to create a material connection of an electrical contact between the strand conductor and a simultaneously or additionally added or deferred pot shaped contact element. The strand conductor can be dipped in a tin bath for applying the contacting means. At the same time, a part of the strand conductor forms a separation or cutting surface which can be separated or cut off in the tin bath. The contact element is pressed around the strand conductor with strain relieving tension.
DE 10 2011 018 353 A1 describes a method for connecting a contact part with an aluminum composed strand conductor. On the end of the strand conductor is placed a protective sleeve and with the same pressed together. Subsequently, a rotationally symmetrical contact part is welded with the front side of the strand conductor, for example by means of rotational welding. As a result, an intermetallic connection between the contact part and the strand conductor is formed.
DE 10 2011 089 207 A1 describes a method for contacting a strand conductor with individual wires composed of, for example, aluminum with a contact part composed of, for example, copper. In a section of the strand conductor in which the individual wires are exposed, the individual wires are compressed and welded together. For both welding processes an ultrasonic welding method, for example, is used. The part of the oxide layer which surrounds the aluminum composed individual wires of the strand conductor stays in place even when the oxide layer is broken up by the ultrasound.
In DE 2 325 294 A can be found a method for manufacturing a contact end from at least one metallic electrical conductor. In a first embodiment a method with an arrangement for treating an electrical conductor is described, in which the vertically arranged point of the conductor is mounted with the exposed end part down. This arrangement of the conductor is provided because through the heated melted metal the surface tension on the vertical conductor part rises and a pear-shaped little lump-like mass is formed. The little lump can be used to form different contact elements by shaping. In a second embodiment of the method, a pair of conductors with upper facing ends are arranged in a clamp. The end of the conductor is melted through the use of an electric arc so that the melted metal can flow from the exposed ends downward and is collected in a hollow in the clamp. The surface tension affecting the melted mass works together with the form of the hollow so that the mass takes on a round symmetrical configuration.
As mentioned above, EP 2 735 397 A1 describes a method for electrically conductively connecting a copper based contact part with an electrical conductor composed of a plurality of aluminum composed individual wires. A pot-shaped contact part has a one-piece cylindrical sleeve protruding from the part. The sleeve is pushed on the conductor until the front surface of the conductor lies on the bottom of the contact part and is there tightly mounted. After that, on the outside of the contact part, for example, in the area of the bottom of the same, a continual pressure rotating tool is attached, which through friction, raises the temperature of the material of the conductor until it softens and diffuses welding it to the contact part.